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Discussion Starter #1
Hi all,

I have done a search across the forum regarding this problem but didn't find anything, so here goes...

When I activate the alarm using the button in the key, everything does what it should, but then the alarm activates itself, seemingly without cause, at any point from a few minutes after activation, up to several hours later. (ie, the middle of the night!)

I tried deactivating the internal ultrasonic sensors, thinking this would eliminate the possibility of the alarm being set off by motion, draughts, insects etc, but it still goes off.

I had a look at the bonnet switch, and that "seems" ok, although very slightly sticky when it rises after being pushed down.

I couldn't find the door or boot switches, so I can't say I've eliminated these.

Can the alarm system be interogated by a specialist to determine any possible faults?

Or can anyone else think of something I've missed?

Any advice greatly appreciated, as I don't like the idea of my pride and joy sitting around without full protection!

Thanks for reading

Mart
 

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Administrator - E46 M3
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my gut instinct would be for the bonnet switch. Should be able to pick up a replacement one, and make sure to seal the bottom of it with silicone. Sometimes water manages to get inside them and make them faulty.

 

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Have you had your battery checked? This happened on an old car of mine - the battery was losing charge after a while, the voltange sensor in the alarm then got triggered and set the whole thing off.
 
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Discussion Starter #4
Many thanks for the replies fellas!

I'll check the bonnet switch again Brian. It *seemed* to be working ok, although it was slightly notchy as the plunger moved back up to its starting position ie, where it would be if the bonnet was opened. Good point about using sealant too!

Kdevitt, I really hadn't thought about the battery, as everything else seems ok, but it's a good point to make. there must be a fine point between just enough and not enough charge, especially in something as sensitive as an alarm system.

If I have any joy I'll be sure to post and let everyone know, because this seems to be quite a common fault with E46's.

Thanks again fellas!

Mart
 
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